Method of dispersing coloring materials in water swellable colloids



Patented Feb. 16, 1943 METHQD F DISPERSING COLORING MATE- BIALS IN WATER SWELLABLE COLLOIDS David E. Bennett, Jr., and Scheuring s. Fierke, Rochester, N. Y., asslgnora to Eastman Kodak Company, Rochester, N. Y., a corporation of v New Jersey No Dra. Application December 26, 1940. Se-

rial No. 371,776. In Great Britain December This invention relates to a methodof dispersing coloring materials in water swellable photographic colloids and particularly to the manufacture of sensitive photographic emulsions containing couplers.

There have been many proposals of methods for incorporating coloring materials such as dyes or color forming compounds in photographic gelatin, particularly sensitive photographic emulsions. When materials such as couplers are incorporated in photographic emulsions, it is usually desirable that the couplers do not difiuse from the layers in which they are incorporated, especially when such layers are used in multilayer coatings. One method of incorporating coloring materials in photographic gelatin layers is described in Mannes & Godowsky U. S. application Serial No. 314,689, filed January 19, 1940. According to the method described in that application, coloring materials such as couplers are mixed with a cellulosic material in the presence of asolvent for the coupler and the cellulosic material and dispersions of the cellulosic material and coupler in gelatin are formed. In preparing these dispersions, it is necessary to remove a part or all of the solvent used to disssolve the cellulosic material and the coupler. First attempts to accomplish the removal of the solvent by spray drying the emulsion containing the coupler produced satisfactory dispersions but resulted in particles of about 4 to 5 microns in diameter and when these were dispersed in gelatin the resulting film was sometimes hazy.

It is, therefore, an object of the present invention to provide a method for incorporating mixtures of coloring materials and water-insoluble colloids in a water-swellable photographic colloid and maintaining the particle size small enough to prevent haze in the resulting film. A further object is to provide a novel method for incorporating couplers in gelatin emulsions. Other objects will appear from the following description of our invention.

These objects are accomplished by dispersing the solution of the coloring material and the water-insoluble colloid in an aqueous vehicle, preferably water or dilute gelatin solution, and removing the solvent from the aqueous dispersion while the particles of coloring material and water-insoluble colloid are in dispersed form.

The coloring material referred to herein may be a dye, a leuco dye or a coupler. By coupler we mean the well known type of color forming compound containing a reactive methylene or phenolic hydrom'l group which is reactive to 12 Claims. (oi. -7)

form a dye in the presence of the oxidized form of primary aromatic amino coupling developers.

The water-swellable or hydrophilic colloid referred to hereinmay be gelatin or agar.

The water-insoluble colloid with which the coloring material is mixed may be a cellulose ester such as collodion or cellulose acetate, a synthetic resin, or a natural gum.

lln preparing the solutions of the coloring material and the water-insoluble colloid, a common solvent is used. By "commonsolvenV we mean a solvent which dissolves both the coupler in its acid or non-water-soluble salt form and the water-insoluble colloid This mixture is dispersed in the presence of a dispersing agent in aqueous solution, the dispersing agent being either gelatin or a material such as a fatty alcohol sulfate.

The method used according to our invention may be conveniently illustrated by reference to the incorporation of a coupler in a gelatin emulsion although it is to be understood that the method is equally applicable to the coloration of other coloring materials such as dyes in other water-swellable colloids such as plain photogaphic gelatin.

Since gelatin is a hydrophilic colloid, couplers are usually incorporated in it by forming the water-soluble sodium salt of the coupler and mixing this with the gelatin or emulsion. According to our process, it is not necessary to form the water-soluble salt of the coupler but the coupler may be incorporated in the emulsion in its acid form. The coupler is mixed with a waterinsoluble material such as collodion in a common solvent such as butyl acetate. This solution is then added to an aqueous solution containing a dispersing agent such as gelatin or a higher fatty alcohol sulfate. The mixture is then treated to form a dispersion of the solution of the coupler and the water-insoluble colloid solution in the aqueous solution. This may be done by passing the mixture through a small homogen-' izer. The suspension formed in this way is heated preferably under vacuum to remove the butyl acetate or other solvent employed in the preparation of solution and coupler and water-insoluble colloid. After the volatile solvent is removed, the suspension of fine particles in the aqueous solution is added to a gelatin emulsion and, after mixing with it, the resulting emulsion is coated. As an alternative, the solvent may be removed after mixture with the gelatin or the solution of coupler and water-insoluble col- Example 1 20 cc. of a commercial collodion emulsion are diluted with 20 cc. of normal butyl acetate and 1.5 grams or 1,4-di-(w-benzoylacetamino)-benzene. This solution was then added to 100 cc. of a 1'2 solution of Gardinol WA in water. Gardinol is a well known dispersing agent of the long chain alcohol sulfate type. The suspension was then recirculated through a small homogenizer for 5 minutes and was vacuum distilled to remove solvents employed in the preparation of collodion emulsion and the butyl acetate which was added. Prior to the removal of the solvent by vacuum, small amounts of N-octyl alcohol were added to prevent foaming. After the volatile solvents were removed, the suspension of the fine particles in the Gardinol solution was added to 50 cc. of a 6% gelatin solution and the samples were coated.

Instead of the Gardinol solution, a gelatin solution can be used.

The whole mixture is heated on a steam bath at 100 C. with constant stirring to evaporate all of the butyl acetate and some of the water. At the end of the evaporation process the volume has been reduced to about 300 cc. This dispersion of cellulose nitrate particles containing the coupler is added to 1000 cc. of a red-sensitive gelatino-silver halide emulsion. The resulting emulsion is coated on a suitable support. A yellow filter layer is then coated on the emulsion, consisting of tartrazine in gelatin.

The top layer consists of a green-sensitive silver halide gelatin emulsion to which has been added a cellulose nitrate dispersion made as described in the preceding paragraph, but using as the coupler a mixture yielding an orange-red dye upon development. Suitable couplers for this purpose are n-propyl-p-benzoyl acetoamino benzene sulfonate and 2-cyanoacetylnaphthalene-sulfon-N-methyl anilide. These couplers are used in the amount of 5 grams each and producing an orange red dye upon development in a coupling developer. This emulsion is coated as the top layer to produce a two-layer sensitive material.

In place of the tartrazine filter dye, the film may contain a yellow dye throughout the emulsions which is removable during processing either by virtue of its solubility or its susceptibility to a chemical action of one of the processing baths.

The method described in the present specification offers advantages over the spray drying procedure from the standpoint both of simplicity and of increased yield. The method is also less hazardous and produces dispersed particles of an average size of one micron or less.

The examples included in the present specification are illustrative only and it is to be understood that our invention is limited only by the scope of the appended claims.

We claim:

1. The method of dispersing a coloring material in a water-swellable photographic colloid which comprises dissolving the coloring material and a water-insoluble colloid in a common solvent which is a non-solvent for the water-swellable colloid, emulsifying the solution in an aqueous solution of a dispersing agent, removing the solvent from the emulsion by evaporation while the particles of coloring material and waterinsoluble colloid are in a dispersed form and suspending the coloring material and waterinsoluble colloid in finely divided form in the water-swellable colloid.

2. The method of dispersing a coloring material in a water-swellable photographic colloid, which comprises dissolving the coloring material and a water-insoluble colloid in a common solvent which is a non-solvent for the water-swellable colloid, emulsifying the solution in thewaterswellable colloid, and removing the solvent by evaporation while the particles of coloring material and water-insoluble colloid are in a dispersed form, thereby leaving the coloring material and water-insoluble colloid suspended in finelydivided form in the water-swellable colloid.

3. The method of dispersing a coloring material in gelatin, which comprises dissolving the coloring material and a water-insoluble colloid in a common solvent which is a non-solvent for the gelatin, emulsifying the solution in water containing a dispersing agent, and removing the solvent by evaporation while the particles of coloring material and water-insoluble colloid are in a dispersed form, thereby leaving the coloring material and water-insoluble colloid suspended in finely-divided form in the aqueous solution, and mixing it with the gelatin.

4. The method of dispersing a coupler in gelatin, which comprises dissolving the coupler and a water-insoluble colloid in a common solvent which is a non-solvent for the gelatin, emulsifying the solution in water containing a dispersing agent, and removing the solvent by evaporation while the particles of coupler and water-insoluble colloid are in a dispersed form, thereby leaving the coupler and water-insoluble colloid suspended in finely-divided form in the aqueous solution, and mixing it with the gelatin.

5. The method of dispersing a coloring material in gelatin, which comprises dissolving the coloring material and cellulose ester in a common solvent which is a non-solvent for the gelatin, emulsifying the solution in water containing a dispersing agent and removing the solvent by evaporation whilethe particles of coloring material and cellulose ester are in a. dispersed form, thereby leaving the coloring material and cellulose ester suspended in finely-divided form in the aqueous solution, and mixing it with the gelatin.

6. The method of dispersing a coupler in gelatin, which comprises dissolving the coupler and collodion in a common solvent which is a nonsolvent for the gelatin, emulsifying the solution in water containing a dispersing agent, and removing the solvent by evaporation while the particles or coupler and collodion are in a dispersed form, thereby leaving the coupler and collodion suspended in finely-divided form in the aqueous solution, and mixing it with the gelatin.

7. The method of dispersing a coupler in gelatin, which comprises dissolving the coupler and a water-insoluble colloid in a common solvent which is a non-solvent for the gelatin, emulsifying the solution in water containing a dispersing agent, and removing the solvent by evaporation under vacuum while the particles of coupler and water-insoluble colloid are in a dispersed form, thereby leaving the coupler and water-insoluble colloid suspended in finely-divided form in the aqueous solution, and mixing it with the gelatin.

8. The method of dispersing a coupler in gelatin, which comprises dissolving the coupler and a water-insoluble colloid in a common solvent which is a non-solvent; for the gelatin, emulsifying the solution in water containing a dispersing agent, and removing the solvent by vacuum distillation while the particles of coupler and waterinsoluble colloid are in a dispersed form, thereby leaving the coupler and water-insoluble colloid suspended in finely-divided form in the aqueous solution, and mixing it with the gelatin.

9. The method of claim 4, in which the solvent is an ester.

10. The method of claim 4, in which the solvent is an ester of a lower fatty alcohol and a lower fatty acid.

11. The method of claim 7, in which a foampreventing agent is added to the emulsion prior to removal of the solvent.

12. The method of dispersing a coupler in a gelatino-silver halide emulsion which comprises dissolving the coupler and a water-insoluble colloid in a common solvent which is a non-solvent for the gelatin of the emulsion, emulsifying the solution in water containing a dispersing agent and removing the solvent by evaporation under vacuum while the particles of the coupler and water-insoluble colloid are in a dispersed form, thereby leaving the coupler and water-insoluble colloid suspended in finely divided form in the aqueous solution and mixing said solution with the gelatino silver halide emulsion.

DAVID E. BENNETT, JR. SCHEURING S. FIERKE. 

